Please find the attached patch for the RM # 6953 - Webserver Authentication: Include headers coming from servers.
In the RM, 2 users have provided the solution, I have merged them.
As per the current behaviour, pgAdmin only considers the REMOTE_USER environment variable (set by the webserver). In this patch, we have introduced the WEBSERVER_REMOTE_USER config variable, so users can modify it as per their environment. Also, we check for the environment as well as request headers for the remote user details.